Sunday, July 26, 2009

Educational unconformity

I find myself in New Hampshire right now because we received a phone call that had the words "dad, brain, surgery and cancer" all in the same sentence. Unfortunately air travel tickets were at a premium so we elected to drive. The drive while long was uneventful but it brought to mind a question poised by a student on my last field class.

How are continents made? Every earthscience teacher in the K12 world teaches about continents. They all explain to their students about how continents "float" while oceanic crust "sinks" They all explain how new oceanic crust is "created" at spreading centers, but none of the group I had ever discussed how continents are made.

A quick survey of my class found that no one really discussed this chapter of geology. I was wondering. Do university classes skip this? Do university students just forget this part? Or has this knowledge level eroded away?

2 comments:

No, university classes don't skip this, but the answer is more complicated than the answer for oceanic crust. (The easy answer is "accretion of island arcs," but explaining the composition of oceanic arcs gets into all kinds of interesting stuff about igneous rocks. I talk about it in my intro class - I've used the question to motivate the discussion of the evolution of igneous rocks - but a lot of students don't get that part.)

(And my graduate advisor would argue that material is added to the continental crust during failed continental rifting, as well - she was always a bit cranky when people simplified continental crust to a bunch of accreated island arcs.)

Kim, I agree that the concept is a little more involved than oceanic crust. And, I don't really believe that University classes skip this part. I was just surprised of the universality of no one knowing even the simplified version.